This invention relates to surgical instruments for use in conjunction with bone fixation components such as pins and wires, and more particularly relates to instruments for the removal of such components.
1. Background of the Invention
It is quite common, when carrying out surgical procedures on bones, particularly in the hands, and also generally in the limbs, to implant a pin or wire into the injured or diseased bone. The purpose of the wire is to reinforce the bone during healing. Particularly in surgery of the hand, where wire is used, an end of the wire may be left protruding from the skin to make it easy to remove the wire later, or the wire may be trimmed below the level of the skin.
2. Description of the Prior Art
Instruments are available for extracting surgical wires and pins. Some such instruments are based on the principle of using a Jacobs"" chuck to tighten the instruments onto the wire, whereupon the wire can be drawn clear of the bone, and discarded. Other instruments are merely special forms of pliers adapted for a particular medical situation.
A problem that arises with most known instruments is that the tissues around the area from which the wire is extracted can become severely traumatised by the manipulation of the wire; and by the manipulation of the extractor so as to attach it to the wire. The reason is that the known instruments have been too heavy and cumbersome and awkward. It has proved to be too difficult for a surgeon to consistently tighten a chuck, using a chuck key, onto the wire with the degree of sensitivity and delicacy that is required to avoid damaging the surounding tissues.
An instrument that is somewhat lighter and easier to use than a typical Jacobs"" chuck is disclosed in U.S. Pat. No. 4,263,903. It comprises a one piece jaw that is contained in a slender body means. In order to close the jaws, it relies on the body means to act on a cam surface located on the outer surfaces of the jaws. As the jaws are pulled up into the body means, they are forced together. The jaws are pulled into the body means by rotating a screw thread assembly. This method of bringing the jaws together takes a longer period of time than is desirable and also requires a great deal of hand movement. It could therefore, cause necessary trauma and tissue damage.
In accordance with one aspect of the present invention, there is provided an instrument for extracting surgical wires, particularly surgical wires such as K-wire(trademark). Surgical wires include such things as wires, pins, staples, and intramedullary nails. The instrument will permit the user to consistently tighten a portion of the instrument onto the wire with the appropriate delicacy. The present invention provides an instrument that can be tightened and otherwise manipulated by the user with the delicacy expected for work of this nature. This is in part due to the tactile feedback experienced by the user. This tactile feedback is a result of the reaction forces generated by the gripping of the pin or wire. These forces are transmitted, at least in part, back to the user""s hand.
In the present invention, the instrument may be operated by a single hand. It is provided with a hand-grip, a cam lever, a pair of jaws, and a collet. The cam lever is operable by the hand while holding the hand-grip. The cam lever draws the jaws, which grip the surgical wire or pin, up into the collet. A tapered surface on the collet acts on the cam surface of the jaws to urge the jaws together. The action of closing the hand is sufficient to perform this action, thus making the gripping action very quick, which is effective in reducing trauma and tissue damage.
It has been found, by this invention, that the combination of the cam lever and the camming action between the jaws and the collet makes it possible to apply a strong gripping force to the jaws in a very controlled manner. The undesired side-forces that could hardly be avoided with the Jacobs"" chuck, are virtually non-existent with this invention. It is these uncontrolled side-forces particularly that typically lead to trauma and tissue damage.
It has also been found to be beneficial that there are only two opposed jaw surfaces, rather than the three wedge-shaped jaw pieces usual to a Jacobs"" chuck.
There is some friction associated with both the tapered collet and cam surface mechanism and the sliding and rubbing cam lever mechanism. It is recognized in the present invention that some friction here is beneficial, since it may be desirable that the gripping force be partially locked in even if the grip on the cam lever should be relaxed. If there were to be a frictionless connection between the jaws and the cam lever, then the grip of the jaws would relax as the force on the cam lever was relaxed.
On the other hand, the friction should not be so great that the magnitude of the jaw gripping force is unduly diminished. It has been found, in the present invention, that the combination of the tapered collet and cam mechanism and the cam lever mechanism gives a suitable degree of friction.
In this invention, the cam lever is operated by the hand that grips the hand-grip. This frees the other hand for the purpose of steadying the instrument, or otherwise manipulating the patient""s body or surgical site using the surgeon""s own hand-eye co-ordination without the need for voice commands to a nurse or other surgical assistantxe2x80x94or indeed, to the patient. This, again, reduces the likelihood of generating side-forces, which would result in trauma or tissue damage.
Additionally, a squeeze grip type of action is one of the easiest ways of applying a large force in a well controlled manner. This is due to the relatively high gripping strength of a human hand and to the fact that the gripping forces are applied roughly co-linearly to the direction of application of gross force during the removal of the surgical wire.
The strength of the grip needed from the instrument, to pull the wire or pin out, can be quite large. Thus, the jaw must be robust enough to withstand a heavy twisting action, because it may be necessary to rotate the instrument to make it easier to extract the wire or pin. The collet and cam combination of the present invention permits construction of an instrument having jaws of sufficient size, and of suitable material, that can easily cope with the noted forces, without undue distortion. In the present invention, all the components of the instruments, though simple to construct, can be sturdy and reliable over a long service life, with none of the components being subject to undue wear.